Sun Microsystems Sun Ultra 60 Service Manual page 200

Figure C–7
C.1.9.2 Serial Port Functions
The serial port provides a variety of functions. Modem connection to the serial port
allows access to the internet. Synchronous X.25 modems are used for
telecommunications in Europe. An ASCII text window is accessible through the serial
port on non-graphic systems. Low speed printers, buttonboxes (for CAD/CAM
applications) and exotic devices that function like a mouse are also accessible
through the serial port. The additional speed of the serial port can be used to execute
communications with a CSU/DSU for a partial T1 line to the internet at 384 Kbaud
per second.
C.1.9.3 EIA Levels
Each serial port supports both RS-232 and RS-423 protocols. RS-232 signaling levels
are between -3 Vdc and -15 Vdc and +3 Vdc and +15 Vdc. A binary 1 (0012) is
anything greater than +3 Vdc and a binary 0 (0002) is anything less than -3 Vdc. The
signal is undefined in the transition area between -3 Vdc and +3 Vdc. The line driver
switches at -10 Vdc and +10 Vdc with a maximum of -12 Vdc and +12 Vdc in RS-232
mode. RS-423 is similar except that signaling levels are between -4 Vdc to -6 Vdc and
+4 Vdc and +6 Vdc. The line driver switches at -5.3 Vdc and +5.3 Vdc with a
maximum of -6 V and +6 Vdc. Switching from RS-232 to RS-423 protocol is
accomplished by changing jumpers J2604 and J2605. Jumper positions 1 and 2 are for
RS-232 and jumper positions 2 and 3 are for RS-423.
Sun Ultra 60 Service Manual ♦ March 1999, Revision A
C-20
Serial Port Functional Block Diagram